Nikola Tesla Books
QUENCHED GAP APPARATUS 101 be varied in length by threading the spindle through the top frame plate 5. This construction presents some very fine machine work, and a screw-cutting lathe is positively essential. Assuming that the latter tool is not to be found in the average amateur shop, the design has been modified so that the threading may all be done with taps and dies, and the only lathe work required is the facing-off and drilling operations that may be done in a small bench lathe with a slide rest. The effects produced with the high-frequency coil in connection with a quenched gap are truly remarkable. Instead of the thin, wiry spark ordinarily seen, the discharge takes the form of a flame as thick as a man's wrist when conditions are right. At times the actual length of the discharge is reduced, but with everything in resonance an increase both of thickness and length will be noted. With reference to Fig. 1, which is a sectional view of the complete gap, the reader will note the instrument is comprised of two cast copper electrodes, 1 and 2, which are held rigidly, with their faces only slightly separated. The lower electrode is permanently secured to the lower iron casting of the frame 6, while the upper electrode is arranged to be raised or lowered by turning the insulated knob 14, which is fastened to a brass bushing 13. The spindle 3, which carries the electrode 2, is of cold rolled steel, threaded 17-18 for a distance of 1 in., when it enters the electrode, then turned to ½ in. for the central portion and finally threaded for 1 in., with the 1-18 die for the remaining portion. The electrode is held from turning by the two steel pins 7, which are driven into holes in the electrode and which slide freely in holes in the frame above. Obviously, therefore, the movement of the upper electrode is a vertical one without any twist or turn. The coiled spring 8, serves
